1. The traditional technique for measuring the properties of the ionosphere by transmission and reception of vertically incident radio pulses at swept frequencies in the high frequency range.
2. A pulsed radar device used to measure the height of ionospheric layers.
3. A radar system for determining the vertical height at which the ionosphere reflects signals back to earth at various frequencies.

A pulsed vertical beam is swept periodically through a frequency range from 0.5 to 20 megahertz, and the variation of echo return time with frequency is photographically recorded.